Heh, I was going through this code a week or so ago and thought this
looked odd...
I'll apply the patch.
On Thu, 12 Jun 2008 14:53:22 +0200, Jose Luis Martinez wrote:
> Hi,
>
> We're using the require_resolvable_fromhost plugin, and have seen
> that there is a bug in it. MAIL FROM commands with legitimate
> domains where getting rejected as not resolvable.
>
> The bug has been tracked down to domains that have zone files with
> unresolvable MX records.
>
> example.com. 3600 IN MX 10 fakeserver.example.com.
> example.com. 3600 IN MX 20 mail.example.com.
> example.com. 3600 IN MX 30 anotherfakeserver.example.com.
>
> The plugin tries to resolve every MX record in the list (to see if it
> has an A record), but gives up on the first unresolvable one,
> considering the whole domain unresolvable.
>
> I consider this a bug, as leaving fake MX records is a known antispam
> technique, and after all, the domain is resolvable if you have at
> least one resolvable MX record.
>
> Patch attached:
>
> Index: plugins/require_resolvable_fromhost
> ===================================================================
> --- plugins/require_resolvable_fromhost (revision 1)
> +++ plugins/require_resolvable_fromhost (working copy)
> @@ -53,8 +53,14 @@
> $res->udp_timeout(30);
> my @mx = mx($res, $host);
> foreach my $mx (@mx) {
> - return mx_valid($self, $mx->exchange, $host);
> + # if any MX is valid, then we consider the domain
> + # resolvable
> + return 1 if mx_valid($self, $mx->exchange, $host);
> }
> + # if there are MX records, and we got here,
> + # then none of them are valid
> + return 0 if (@mx > 0);
> +
> my $query = $res->search($host);
> if ($query) {
> foreach my $rrA ($query->answer) {
>
>
> Jose Luis Martinez
> [EMAIL PROTECTED]
> CAPSiDE
>
